Additive gearshift with differential gears

ABSTRACT

This invention is a mechanical gearbox for every vehicle or machinery that needs one. It works on the grounds of the differential gear as a way to obtain mechanical addition or subtraction of the motion of two different shafts. Inside this mechanism an input-shaft-motion subdivision take place over other different shafts, which speeds are recombined together by differential gears, returning over an output-shaft a wide-range of selectable speeds with their proportional torque (transmission ratios).

BACKGROUND OF THE INVENTION

Basically there are 3 main types of gearboxes: manually shifted gearboxwith a maximum of about 20 speeds for trucks and 6 for cars; gearboxwith planetary gear sets; and continuously variable transmission (CVT).

BRIEF SUMMARY OF THE DISCLOSURE

This invention can be catalogued as a MECHANICAL GEARBOX, but comparedwith the usual gearbox, this one has nearly the advantages of a CVT's(continuously variable ratio transmission) for its high number ofobtainable speeds. The speed-range is very wide and the gap between thevarious speeds can be very small.

The gearbox of the present invention is extremely versatile and can beconfigured in different ways by small variants in the construction ofthe gearbox. It is possible to obtain, for example, all forward gears,one reverse gear and all remaining forward gears, more reverse gears, oras many reverse gears as forward gears with the same ratios.

The rotational velocity of the output is selected by engaging ordisengaging one or more clutches inside the gearbox, and the procedureis fast without the need of a main friction clutch. A neutral gear isalso available.

With a single rotational velocity of the input, the gearbox of thepresent invention is able to output many speed-levels. The number ofspeeds depends on the number of differential gears employed, forexample, 1 differential=3 speeds; 2 differential=7 speeds; 3differential=15 speeds; 4 differential=31 speeds; and so on. In thisinvention, the task of the differential gear is simply to add the speedof two different input shafts rotating in the same direction, and returnas an output on a third shaft, the right value of speed with itsproportional torque.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, side view of a differential gearbox;

FIGS. 2.1–2.4 illustrate the overall principle of the present invention,including four examples, showing how it would be possible to connecttogether 1 to 4 differential gears in order to get 3 to 31 differentspeed ratios;

FIG. 3.1 is a schematic illustration of how clutches are employed in thepresent invention;

FIG. 3.2 illustrates a simply coding arrangement for controlling theclutches of FIG. 3.1 to obtain various rotational velocities at theoutput shaft; and

FIG. 4 is a schematic illustration of one embodiment of the invention.

FIG. 1 illustrates a prior art differential gearbox used to makeadditions. A and B are input shafts which rotate in the same direction.The speed of shaft B has been reduced by 50% of that of shaft A by gearsR1 and R2. Gear R1 is bored out in the center to allow free passage ofthe input shaft A through gear R1. Gear R1 is fixed to rotate with thedifferential gearbox SCD. Two free-wheels RL are mounted on each ofinput shafts A and B in order to prevent them from rotating in thedirection opposite to the normal rotating direction. In the case whereone of the two input shafts is stationary and there is a load on theoutput shaft C, without free-wheels the stationary input shaft wouldstart rotating in the opposite direction and no torque would come fromoutput shaft C.

The rotational velocity of the output shaft C will be exactly the sum ofthe rotational velocities of shafts A and B, but with an oppositerotating direction. RC are four conical gears. Free-wheels are notabsolutely necessary in the invention, they are just one way to solvethe problem discussed above.

Now, to an overall principle scheme of the gearbox of the presentinvention. FIGS. 2.1–2.4 illustrate four examples showing how it wouldbe possible to connect 1 to 4 differential gears in order to get 3 to 31different speed ratios. As can be seen an important part of themechanism consists in the gear train TR put before the differentialgears. Input shafts to the differential gears come from TR andrespectively from left to right, each one rotates at the previous one'shalf speed. As shown in the drawings, the input shafts connected to thedifferential gears are identified with the ratio numbers of theirrelative speeds. The lowest number is 1 which is the lowest speed andwhich also represents the minimum increase unit of the final output US.

For purposes of explanation and because of its average complexity andnumber of output speeds, the 3-differential gears and 4-input shaftsgearbox shown in FIG. 2.3 will be discussed.

The example of FIG. 2.3 shows a 15 speed gearbox. It provides 15 speedswith ratios from 1 to 15, increasing from speed to speed always by 1.There are four possible input shafts IN to the gearbox. Each input shaftIN is connected to the gear train TR. Where input shaft 8 is driven at80 rpm by a motor, it is possible for the output shaft US to be drivenwithin a speed range from 10 to 150 rpm, increasing from speed to speedby 10 rpm. The input shaft 1 at the far right is always the minimumincrease unit (as previously described). As another example, if an 80rpm motor is connected to input shaft 1, a speed range from 80 to 1200rpm, with an increment of 80 rpm, is obtainable from output shaft US.

In order for the invention to operate properly clutches are essential toengage any speed. As FIG. 3.1 shows, every input shaft, between the geartrain TR and the differential gear D, is provided with a clutch INN.Clutches block or transmit the motion of the individual input shafts, 8,4, 2, 1 to the differential gears as needed, and combined together theydetermine every possible speed. Every single possible combination isassured by a simple table (FIG. 3.2), calculated on the grounds of thebinary number system. The table shows clutch states according to thespeed to be engaged. On the horizontal axis, there is represented theinput shafts; on the vertical axis, there is represented the speednumbers. The black dot indicates motion transmission through the clutch,and the white dot indicates no motion transmission.

The clutches used must be DUAL-ACTION type, that is, they must have twodifferent states: the first one is motion transmission; the second oneis no motion transmission and they must also lock, in both rotatingdirections, the part of the shaft entering into the differential gearand get it in sympathy with the gearbox SCC (FIG. 3.1).

Up to now, all that has been explained is a theoretical explanation ofthe invention. Its practical realization will be different from somepoints of view due to the absolute necessity to respect the rotatingdirections of every single shaft inside the gearbox. It is veryimportant for the right operation of the invention.

According to the rotating directions of the two input shafts in adifferential gear used to make additions (as FIG. 1), from the outputshaft C, we can get an addition or a subtraction. Now if we shape thegearbox combining additions and subtractions, as output we obtain aspeed range including reverse gear. It is also possible to obtain manydifferent reverse gears, but the total number of speeds is 15 plus aneutral gear. The obtainable configurations are various.

From now on, for purposes of explanation, the 3 differential gearsinside the gearbox are all addition type (“+” sign in FIG. 3.1).Consequently all forward 15 speeds are available.

FIG. 4 shows an overall view of an actual mechanism for carrying out theinvention. There are some changes compared with FIG. 1 and FIG. 3.1: onthe gear train TR and on both internal gears RDI of the differentialgears D1 and D2. The reason is simple. In FIG. 1, input shafts A and Brotate in the same direction (obligatory condition to obtain additions).Nevertheless, a 4-shafts gear train as FIG. 3.1 inverts the rotatingdirection from one shaft to another, so we could never obtain twoadjoining shafts with the same rotating direction. That is why theinternal gear is necessary: like chains or belts, it does not reversethe motion.

However, using this type of gear, it is not possible to obtain a 50%reduction ratio (as FIG. 1) between R3 and RDI, because of theencumbrance of the shaft going into the differential gear. So, we canobtain a one-third reduction ratio, but the difference must becompensated by changing gear train ratios. On TR, we shall obtain anirregular sequence of different ratios that, if correctly calculated,are equivalent to the theoretical ones in FIG. 3.1.

Gears R1 and R2 have a 50% reduction ratio. R1 is in sympathy with thedifferential box of D3, and it is bored out in the center to allow freepassage to the shaft coming from D1. It is the same with RDI. SCC is thegearbox that clutches INN (not drawn in every detail) are locked to. SCDare differential boxes that gears RDI and R1 are in sympathy with. Thedifferential gear D3 has not been drawn in every detail, but it isexactly identical to D1 and D2. RC are 4 conical gears inside eachdifferential box. US is the final output shaft, and it rotates in thesame direction as the input shaft IN.

The foregoing relates to preferred exemplary embodiments of theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

1. A transmission system for combining rotational velocities from afirst and a second rotating shaft and transmitting a combined sum of therotational velocities to an output shaft, said first shaft being drivenat a rotational velocity V, a gear system interconnecting said first andsecond rotating shafts and for driving the second rotating shaft at arotational velocity which is approximately 0.5V, a clutch associatedwith each of said rotating shafts, each of said clutches having a firststate in which rotary motion is transmitted as an output, and a secondstate in which no rotary motion is transmitted, a first differentialgear box receiving the rotary motion outputted by one or more of saidclutches, and transmitting rotary motion to said output shaft, saidoutput shaft being driven by said differential gear box at a rotationalspeed which is approximately equal to: 0, if the clutches associatedwith said first and second rotating shafts are in said second state: V,if the clutch associated with said first rotating shaft is in said firststate and the clutch associated with said second rotating shaft is insaid second state: 0.5V, if the clutch associated with said firstrotating shaft is in said second state and the clutch associated withsaid second rotating shaft is in said first state; or 1.5V, if theclutches associated with said first and second rotating shafts are insaid first state, including a third rotating shaft, said gear systeminterconnecting said first, second and third rotating shafts for drivingthe third rotating shaft at a rotational velocity which is approximately0.25V, a clutch associated with said third rotating shaft and a seconddifferential gear box, said first differential gear box receiving anoutput from the clutches associated with the first and second rotatingshafts, and the second differential gear box receiving an output fromthe clutch associated with said third rotating shaft and an output fromsaid first differential gear box, said output shaft being driven by saidsecond differential gear box within a rotational speed range ofapproximately 0 to 1.75V, depending on the state of said clutches. 2.The transmission system of claim 1, wherein the rotational speed of saidoutput shaft varies within said rotational speed range, according to thestate of said clutches, in increments equal to 0.25V.
 3. A transmissionsystem for combining rotational velocities from a first and a secondrotating shaft and transmitting a combined sum of the rotationalvelocities to an output shaft, said first shaft being driven at arotational velocity V, a gear system interconnecting said first andsecond rotating shafts and for driving the second rotating shaft at arotational velocity which is approximately 0.5V, a clutch associatedwith each of said rotating shafts, each of said clutches having a firststate in which rotary motion is transmitted as an output, and a secondstate in which no rotary motion is transmitted, a first differentialgear box receiving the rotary motion outputted by one or more of saidclutches, and transmitting rotary motion to said output shaft, saidoutput shaft being driven by said differential gear box at a rotationalspeed which is approximately equal to: 0, if the clutches associatedwith said first and second rotating shafts are in said second state; V,if the clutch associated with said first rotating shaft is in said firststate and the clutch associated with said second rotating shaft is insaid second state; 0.5V, if the clutch associated with said firstrotating shaft is in said second state and the clutch associated withsaid second rotating shaft is in said first state; or 1.5V, if theclutches associated with said first and second rotating shafts are insaid first state, including a third rotating shaft and a fourth rotatingshaft, said gear system interconnecting said first, second, third andforth rotating shafts for driving the third rotating shaft at arotational velocity which is approximately 0.25V and for driving saidfourth rotating shaft at a rotational velocity which is approximately0.125V, a clutch associated with said third rotating shaft, a clutchassociated with said fourth rotating shaft, a second differential gearbox and a third differential gear box, said first differential gear boxreceiving an output from the clutches associated with the first andsecond rotating shafts, and the second differential gear box receivingan output from the clutch associated with said third and fourth rotatingshafts, and said third differential gear box receiving an output fromsaid first and second differential gear boxes, said output shaft beingdriven by an output of said third differential gear box within arotational speed range of approximately 0 to 1.875V, depending on thestate of said clutches.
 4. The transmission system of claim 3, whereinthe rotational speed of said output shaft varies within said rotationalspeed range, according to the state of said clutches, in incrementsequal to 0.125V.
 5. A transmission system for combining rotationalvelocities from a first and a second rotating shaft and transmitting acombined sum of the rotational velocities to an output shaft, said firstshaft being driven at a rotational velocity V, a gear systeminterconnecting said first and second rotating shafts and for drivingthe second rotating shaft at a rotational velocity which isapproximately 0.5V, a clutch associated with each of said rotatingshafts, each of said clutches having a first state in which rotarymotion is transmitted as an output, and a second state in which norotary motion is transmitted, a first differential gear box receivingthe rotary motion outputted by one or more of said clutches, andtransmitting rotary motion to said output shaft, said output shaft beingdriven by said differential gear box at a rotational speed which isapproximately equal to: 0, if the clutches associated with said firstand second rotating shafts are in said second state; V, if the clutchassociated with said first rotating shaft is in said first state and theclutch associated with said second rotating shaft is in said secondstate; 0.5V, if the clutch associated with said first rotating shaft isin said second state and the clutch associated with said second rotatingshaft is in said first state; or 1.5V, if the clutches associated withsaid first and second rotating shafts are in said first state, includinga third, a fourth and a fifth rotating shaft, said gear systeminterconnecting said first, second, third, forth and fifth rotatingshafts for driving the third rotating shaft at a rotational velocitywhich is approximately 0.25V, for driving said fourth rotating shaft ata rotational velocity which is approximately 0.125V, and for drivingsaid fifth rotating shaft at a rotational velocity which isapproximately 0.0625V, clutches associated with said third, fourth andfifth rotating shafts, a second, a third, and a fourth differential gearbox, said first differential gear box receiving an output from theclutches associated with the first and second rotating shafts, thesecond differential gear box receiving an output from the clutchassociated with said third and fourth rotating shafts, the thirddifferential gear box receiving an output from said first and seconddifferential gear boxes, and the fourth differential gear box receivingan output from said third differential gear box and an output from theclutch associated with said fifth rotating shaft, said output shaftbeing driven by an output of said fourth differential gear box within arotational speed range of approximately 0 to 1.94V, depending on thestate of said clutches.
 6. The transmission system of claim 5, whereinthe rotational speed of said output shaft varies within said rotationalspeed range, according to the state of said clutches, in incrementsequal to 0.0625V.